[Bug testsuite/65116] [4.9/5 Regression] additional_sources not defined anymore during dg-final

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65116

--- Comment #6 from vries at gcc dot gnu.org ---
I reproduced the issue in the description field with and without Maxim's patch,
so AFAIU it's an orthogonal issue.